Lean body mass is an important determinant of resting and 24-hour energy expenditure. Individuals who suffer spinal cord injuries experience a marked loss of muscle mass which may decrease energy expenditure and promote an increase in body fat. This project tests the hypothesis that energy expenditure is decreased in patients with spinal cord injuries as a consequence of their marked muscle atrophy. Resting metabolic rate will be measured by indirect calorimetry and body composition by dual- energy X-ray absorptiometry (DXA) in subjects with spinal cord injuries and compared to results obtained in age-matched able-bodied individuals. In addition, 24-hour energy expenditure will be measured in a respiratory chamber in a subgroup of paraplegic individuals who are fully independent in self care. A better understanding of the relationship between changes in body composition and energy expenditure in patients with spinal cord injuries may eventually suggest strategies to reduce the excess risk of diabetes and cardiovascular disease in this population. These studies also may improve our understanding of the contributions of muscle mass to energy expenditure in the general population as well as in other special populations characterized by a loss of muscle mass (such as the elderly).